1. Field of the Invention
The invention relates to the field of magnetic bubble devices and particularly the formation of magnetic members on an insulative layer in bubble memories.
2. In the fabrication of magnetic bubble memories, permalloy members are formed on an insulative layer. Often a silicon dioxide layer is formed over conductive members and then the permalloy members are formed on the silicon dioxide layer. When the silicon dioxide layer is formed over the conductive members, rounded regions occur in the silicon dioxide layer along the edges of the underlying conductive members. When the permalloy members are formed over these rounded regions, they include somewhat vertical sections, which as will be described in conjunction with FIGS. 1 and 3, are undesirable.
In the prior art to prevent the formation of the rounded regions in the insulative layer, the edges of the underlying conductive members are tapered. A well-known acid etching process is used to obtain this taper. When the insulative layer is formed over these conductive members, it is generally smoother in the region of the edges of the conductive members. The permalloy members formed on this insulative layer are flatter.
Typically, with this prior art etching process a taper of approximately 1/2 micron (measured in the horizontal direction) is obtained along the edges of the conductive members. Where conductive members are approximately 4 microns wide, this prior art process works well. However, where narrower members are used (e.g., two microns) too much of the conductive material is lost in the taper. This, of course, degrades the electrical performance of the conductive members.
As will be seen, the present invention provides a process for removing the rounded regions in the insulative layer (without tapering the sides of the underlying conductive members).